This invention relates to nondestructive testing and, more particularly, to nondestructive determinations of sphericity of objects such as roller balls.
Ball bearings are a standard rolling contact bearing type for use in transferring loads between rotating and stationary members and in permitting relative rotation with a minimum of friction. Roller balls rotate between two raceways to provide only rolling friction between the relatively moving surfaces. The roller balls are manufactured with extremely tight tolerances on the sphericity of the balls in order to provide a low rolling friction and to provide the thousands of operating hours for which ball bearings are typically designed.
Nondestructive examination (NDE) devices for spherical objects, such as roller balls, currently include micrometers, roundness gages, optical, and electron-optical devices. These devices may be accurate to parts per million or less but they cannot process the quantities of roller balls produced by state-of-the art techniques. Use of the measuring devices is time consuming, typically requiring from 15 min. to 1.5 hr. to determine the sphericity of a ball. Further, the devices measure only discrete locations on the balls and do not accurately describe the entire body of a sampled ball. Thus, sampling techniques are only available to statistically inspect production quantities of roller balls such that individual defective balls may be installed in roller bearings with a concomitant increase in operating friction and reduction in operating lifetime.
These inspection problems are addressed by the present invention and a resonant ultrasound spectroscopy (RUS) technique is presented for examining quantities of roller balls made in a production run. It is therefore an object of the present invention to provide for inspecting roller balls at a rate consistent with the manufacturing process.
It is an object of the present invention to provide an inspection technique that provides a sensitivity compatible with roller ball standards.
Yet another object of the present invention is to adapt RUS techniques to the inspection of production quantities of roller balls.
A further object of the present invention is to provide a roller ball inspection process that characterizes the entire body regardless of orientation in an inspection device.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.